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3 The cell as the basic unit of life • 3.1 Discovery of cells (Extension) • 3.2 Microscope (Extension) • 3.3 Basic structure of a cell • 3.4 The similarities and differences between plant and animal cells • 3.5 The cell as a basic unit of life • Mind Map 3.1 Discovery of cells 3.1 Discovery of cells 1665 Robert Hooke Bark Take a piece of cork Microscope 3.1 Discovery of cells 1665 Robert Hooke Bark Take a piece of cork Microscope 3.1 Discovery of cells 1665 Robert Hooke Microscope Cork cells 3.1 Discovery of cells In early 1800s, Schleiden, Schwann & Virchov suggested 3.1 Discovery of cells Three rules of cell theory : All living things consist of cells The cell is the basic unit of structure and function in all living things Every cell originates from another preexisting cell 3.2 Microscope 3.2 Microscope light microscope dissection microscope electron microscope 3.2 Microscope Eyepiece Magnification light microscope Objective 3.2 Microscope Body tube light microscope Holds eyepiece & objectives 3.2 Microscope Revolving nosepiece light microscope can be rotated to bring the objective into line 3.2 Microscope Coarse adjustment to raise or lower the body tube for focusing light microscope 3.2 Microscope Stage light microscope supports the slide & allows the light to reach the specimen 3.2 Microscope Clip light microscope holds the slide in position on the stage 3.2 Microscope Mirror light microscope reflects light from a light source 3.2 Microscope Iris diaphragm light microscope regulates the amount of light passing through the condenser 3.2 Microscope Arm Base light microscope 3.2 Microscope Summary light microscope eyepiece 4 coarse 1 adjustment arm 2 body5tube revolving6nosepiece objective 7 stage 8 base 3 iris diaphragm 9 mirror 10 3.2 Microscope Experiment 3.1 Using a light microscope A. Low Power Observation 3.2 Microscope Low power observation low power eyepiece 1. Insert the low power eyepiece into the top of the body tube 3.2 Microscope Low power observation 2. Adjust the mirror to reflect light through the hole in the stage mirror 3.2 Microscope Low power observation 3. Adjust the condenser & diaphragm to change the amount of light condenser & iris diaphragm 3.2 Microscope Low power observation 4. Select a low power objective 3.2 Microscope Low power observation 5. Place the slide onto the stage 3.2 Microscope Low power observation 6. While watching from the side, use the coarse adjustment to lower the objective until it is just above the slide 3.2 Microscope Low power observation 7. While looking through the eyepiece, carefully turn the coarse adjustment in the other direction until the object is in focus 3.2 Microscope B. High Power Observation 3.2 Microscope High power observation 1. Observe the specimen with low power first 2. Move the slide so that the part to be observed is at the centre of view 3.2 Microscope High power observation 3. Rotate the revolving nosepiece until 40X objective clicks into position 3.2 Microscope High power observation 4. Adjust the fine adjustment only until the object is in focus 3.2 Microscope High power observation 5. Adjust mirror, condenser & diaphragm to increase the light intensity 3.2 Microscope What are the properties of microscopic images? bigger inverted 3.2 Microscope bigger = Magnification = Eyepiece magnification x objective magnification 3.2 Microscope Magnification = Eyepiece magnification x objective magnification Eyepiece magnification Objective magnification Magnification 5X 40 X 200 X 10 X 10 X 100 X 15 X 40 X 600 X 3.2 Microscope What are the properties of microscopic images? bigger inverted 3.2 Microscope inverted Specimen d Image How ? p 3.2 Microscope inverted Specimen Image p 3.2 Microscope inverted Specimen o 180 Image p 3.3 Basic structure of a cell 3.3 Basic structure of a cell Plant cell Cell wall Chloroplast Cytoplasm Nucleus Vacuole Mitochondrion Cell membrane 3.3 Basic structure of a cell Cell wall is made up of Cellulose 3.3 Basic structure of a cell Cell wall Feature Function Hard Protect & support Large spaces between the cellulose fibers Allow large particles to penetrate the cell wall 3.3 Basic structure of a cell Plant cell Cell wall Chloroplast Cytoplasm Nucleus Vacuole Mitochondrion Cell membrane 3.3 Basic structure of a cell Protein & lipid consists of Cell membrane Control the movement of materials in or out of the cell 3.3 Basic structure of a cell Control Cell membrane is selectively permeable the movement of materials in or out of the cell 3.3 Basic structure of a cell Plant cell Cell wall Chloroplast Cytoplasm Nucleus Vacuole Mitochondrion Cell membrane 3.3 Basic structure of a cell an aqueous solution of many substances e.g. protein consists of Cytoplasm clear, jelly-like provides a medium for chemical reactions to take place contains a lot of organelles & granules 3.3 Basic structure of a cell Plant cell Cell wall Chloroplast Cytoplasm Nucleus Vacuole Mitochondrion Cell membrane 3.3 Basic structure of a cell Chloroplast absorbs sunlight for photosynthesis contains chlorophyll 3.3 Basic structure of a cell Plant cell Cell wall Chloroplast Cytoplasm Nucleus Vacuole Mitochondrion Cell membrane 3.3 Basic structure of a cell bounded by a nuclear membrane Nucleus contains chromosomes made up of DNA control activities of cell 3.3 Basic structure of a cell Plant cell Cell wall Chloroplast Cytoplasm Nucleus Vacuole Mitochondrion Cell membrane 3.3 Basic structure of a cell Respiration takes place Mitochondrion release energy 3.3 Basic structure of a cell Plant cell Cell wall Chloroplast Cytoplasm Nucleus Vacuole Mitochondrion Cell membrane 3.3 Basic structure of a cell large, at the centre Vacuole contains a solution of sugars, proteins and minerals provides support when it is fully filled with water 3.3 Basic structure of a cell contains crystals of insoluble waste Non-living granules starch granules 3.3 Basic structure of a cell Difference ? Plant Cell Animal Cell small vacuole no chloroplast no cell wall 3.3 Basic structure of a cell Summary Animal Cells Cytoplasm 1. mitochondria 2. non-living granules e.g. glycogen (in animal cells only) e.g. starch (in plant cells only) 3. chloroplast (in plant cells only) Cell membrane Plant Cells Nucleus 1. bounded by a nuclear membrane 2. contains chromosomes Cell wall (in plant cells only) 3.4 The similarities and differences between plant and animal cells 3.4 The similarities and differences between plant and animal cells Shape regular irregular Nucleus peripheral centre Cell wall present absent Vacuole large small or absent Chloroplasts present absent Food reserves starch glycogen 3.4 The similarities and differences between plant and animal cells Both plant cells & animal cells contain a cell membrane surrounding the cytoplasm a nucleus mitochondria 3.4 The similarities and differences between plant and animal cells Experiment 3.2 Preparing temporary slides of the plant and animal tissues A. Onion epidermal cells fleshy scale leaf of onion bulb 1. Peel off a small piece of epidermis from the inside of a scale leaf of an onion. forceps 3.4 The similarities and differences between plant and animal cells Experiment 3.2 Preparing temporary slides of the plant and animal tissues A. Onion epidermal cells 2. Cut it to a suitable size, about 5mm2. 3.4 The similarities and differences between plant and animal cells Experiment 3.2 Preparing temporary slides of the plant and animal tissues A. Onion epidermal cells iodine solution 3. Spread the tissue flat on a clean slide and add one drop of iodine solution on top of it. epidermis 3.4 The similarities and differences between plant and animal cells Experiment 3.2 Preparing temporary slides of the plant and animal tissues A. Onion epidermal cells cover slip 4. Gently cover it with a cover slip and make sure no air bubbles are trapped in it. Then examine the slide under the low power of a microscope. 3.4 The similarities and differences between plant and animal cells Experiment 3.2 Preparing temporary slides of the plant and animal tissues B. Ox corneal cells slide ox eye 1. Gently touch the surface of an ox cornea with a clean slide. 3.4 The similarities and differences between plant and animal cells Experiment 3.2 Preparing temporary slides of the plant and animal tissues B. Ox corneal cells methylene blue stain 2. Add a drop of methylene blue stain on the slide. 3.4 The similarities and differences between plant and animal cells Experiment 3.2 Preparing temporary slides of the plant and animal tissues B. Ox corneal cells cover slip 3. Gently cover it with a cover slip. Then examine the slide under the low power of a microscope. 3.4 The similarities and differences between plant and animal cells Experiment 3.2 Preparing temporary slides of the plant and animal tissues C. Hydrilla leaf 1. Put a drop of water on a clean slide. water slide 3.4 The similarities and differences between plant and animal cells Experiment 3.2 Preparing temporary slides of the plant and animal tissues C. Hydrilla leaf Hydrilla 2. Put a piece of Hydrilla leaf into it. Gently cover it with a cover slip. Look at it under the low power of a microscope. 3.4 The similarities and differences between plant and animal cells Experiment 3.2 Preparing temporary slides of the plant and animal tissues D. Pollen grains 1. Take a big flower with ripe stamens. Touch the anther with sellotape. pollen grains anther 3.4 The similarities and differences between plant and animal cells Experiment 3.2 Preparing temporary slides of the plant and animal tissues D. Pollen grains sellotape 2. Stick the pollen grains onto a slide. Look at it under a microscope. slide 3.4 The similarities and differences between plant and animal cells Experiment 3.4 Measuring and comparing the size of plant and animal cells Method of measuring the size of the cells 1. Put a transparent ruler on the stage of a microscope. Move the ruler into the centre of the field of view. Measure the diameter of the field of view. For example, in the diagram, the diameter is 3.5mm . 3.4 The similarities and differences between plant and animal cells Experiment 3.4 Measuring and comparing the size of plant and animal cells Method of measuring the size of the cells 2. Still using the microscope, observe a slide containing plant cells to be measured. Count the number of cells (end to end ) it takes to span the diameter of the field of view. In the diagram, 14 cells span the field of view. Therefore the average cell size is 3.5 ÷ 14 = 0.25mm. 3.5 The cell as a basic unit of life 3.5 The cell as a basic unit of life with different shapes Muscle cell Epithelial cell Nerve cell 3.5 The cell as a basic unit of life Cells Tissue level Three levels of organisation Organ level of cell System level 3.5 The cell as a basic unit of life Cells A tissue is a group of similar cells working together as a unit Tissue level Muscle cell Epithelial tissue Muscle tissue Epithelial cell 3.5 The cell as a basic unit of life Cells Tissue level Animal Tissue Plant Tissue muscular tissue mesophyll tissue connective tissue vascular tissue epithelial tissue epithelial tissue nervous tissue 3.5 The cell as a basic unit of life Cells Tissue level Organ level 3.5 The cell as a basic unit of life Cells Tissue level Organ level Connective Epithelial Muscular Blood tissue Stomach An organ is composed of several different tissues group together to make a functional unit 3.5 The cell as a basic unit of life Cells Tissue level Examples of Organ level organs in mammals organs in plants heart leaves stomach stems eyes roots kidneys flowers lungs fruits 3.5 The cell as a basic unit of life Cells Tissue level Organ level System level Several organs and tissues working together to form a system. These organs and tissues are co-ordinated in the organisms. 3.5 The cell as a basic unit of life Digestive system mouth + oesophagus + stomach + small intestine + large intestine Mind Map working together to form Cells can be observed with consist of microscope Animal cells Plant cells contain tissues contain working together to form nucleus cytoplasm vacuole contains contains chromosomes function control cells’ activities mitochondria are used in respiration cell membrane cell sap contains function support the cells non-living granules which are food or waste materials function control of materials in and out of the cell chloroplasts (in plant cells only) are used in photosynthesis cell wall function support and prevent entry of excess water organs working together to form system